Mr. Knight and other evangelicals say Republicans have failed to deliver on the abortion issue, and they are weighing their electoral options this year. Sen. John McCain could be dealt a major blow if the liberal evangelical movement expands and persuades voters to embrace Mr. Obama or sit out the election.

"We did what they said to do. We elected all these people, we got conservative justices appointed at the bench, and nothing happened," said Tony Jones, the 40-year-old leader of Emergent Village, a national group that often speaks for more liberal Christians from an evangelical background.

Those evangelicals are suffering from "fetus fatigue" and want to "give up," said Douglas Groothuis, a philosophy professor at Denver Seminary.